Drug delivery devices allowing for multiple dosing of a required dosage of a liquid medicinal product, such as liquid medicaments, and further providing administration of the liquid to a patient, are as such well-known in the art.
Drug delivery devices of this kind have to meet a number of user specific requirements. For instance in case of those with diabetes, many users will be physically infirm and may also have impaired vision. Therefore, these devices need to be robust in construction, yet easy to use, both in terms of the manipulation of the parts and understanding by a user of its operation. Further, the dose setting must be easy and unambiguous and where the device is to be disposable rather than reusable, the device should be inexpensive to manufacture and easy to dispose. In order to meet these requirements, the number of parts and steps required to assemble the device and an overall number of material types the device is made from have to be kept to a minimum.
Typically, the medicament to be administered is provided in a cartridge that has a moveable piston or bung mechanically interacting with a piston rod of a drive mechanism of the drug delivery device. By applying thrust to the piston in distal direction, a certain amount of the medicinal fluid is expelled from the cartridge.
With many drug delivery devices of pen-injector type, a user has to depress a dose button, typically located at a proximal end section of the pen housing, in an axial distal direction. In practical use, the dose button is typically to be depressed by a user's thumb while the residual fingers of the same hand grip the housing of the drug delivery device. Furthermore, where an injection force is exclusively to be derived from a user-applied driving force, the handling of a proximal dose button can become problematic, in particular for users suffering side effects or being otherwise handicapped to press the dose button, e.g. by way of a thumb.